Cane sugar is usually traded in granulated form and is classified into different qualities according to its content of impurities, i.e., non-sucrose substances that mainly contribute to increase the rate of color and ashes which come from mineral elements such as potassium, magnesium, sulphates and phosphates, among others (Cane Sugar Manual, James C. P. Chen, Ed. Limusa, 2004, p 56).
As an industrial component, sugar is used for different processes and some users require it in the form of syrup to incorporate it into their processes, therefore, they perform a dilution in water in order to obtain sucrose syrup and then they process it in order to purify it, obtaining what is commonly called liquid sugar. The quality of the liquid sugar to be manufactured is determined by the quality of the granulated sugar used as raw material, the quality of the dilution water, and the type of process used to purify the syrup. When users require liquid sugar with refined sugar quality, they get the product dissolving refined granulated sugar with treated water, which implies additional processes in order to prepare the raw material, thus increasing production costs.
Refined granulated sugar obtained from cane juice is manufactured at sugar mills in two phases: the first phase produces low-purity granulated sugar called raw sugar, which is purified in the second phase. The first phase mainly consists of obtaining and clarifying the cane juice, concentrating and crystallizing the sucrose, centrifuging and drying sucrose crystals, thus obtaining raw sugar, which specifications of color and ashes are quite variable, both due to variations in the raw material used in its manufacturing and the clarification degree of the cane juice and the centrifugation of the sucrose crystals performed during the process. The Mexican Standard NMX-F-084-SCFI-2004 specifies as “standard sugar” the raw sugar with a maximum of 600 ICUMSA (International Commission for Uniform Methods of Sugar Analysis) color units and a maximum ICUMSA conductimetric ash content of 0.25%. The second phase, usually called refining, consists of purifying raw or standard sugar, dissolving again the raw granulated sugar in order to submit it again to various processes, such as: clarifying, filtering, carbonating, activated carbon bleaching, concentrating, crystallizing, centrifuging and drying, in order to obtain the product called refined sugar which specifications on impurity contents are usually below 45 ICUMSA units for color and 0.04% of ICUMSA conductimetric ashes, as specified in the Mexican Standard NMX-F-003-SCFI-2003.
Given the fact that certain users require sugar in the form of refined liquid sugar, it is not necessary to apply the re-dissolving and re-crystallizing process for its refining, as performed by sugar mills through the processes of dissolving, clarifying, filtering, carbonating, activated carbon bleaching, concentrating, crystallizing, centrifuging and drying raw or standard granulated sugar; since refined sugar in liquid form may be produced by purifying the syrup manufactured with raw sugar with a process such as that presented in this invention.
Usual purification processes applied to sugar syrups generally use ion-exchange resins (U.S. Pat. No. 2,578,938 and U.S. Pat. No. 2,785,998), which help remove anions and cations that are to be separated, which constitute impurities regarding the content of ashes and color of the sugar. However, these patents are not focused on the complete process of manufacturing purified liquid sugar.
Patent (GB984713) claims a process to purify 50 to 65% sucrose sugar solutions through bleaching and demineralization processes through ion exchange. The main purpose of this process is to reduce the growth of yeast and fungi, presenting a demineralization process at a temperature of 40-42° C. This is a disadvantage, since that is a relatively low temperature which produces greater viscosity in the syrup, with the resulting hydrodynamic problems for its handling, which eventually derives in increasing operation costs. Unlike this process, the process proposed in our invention considers working with syrup at a concentration preferably above 65% and a temperature between 65 and 70° C., with additional processes besides bleaching and demineralization such as: filtering and sanitizing with ultra violet rays, which contribute to inhibit the growth of fungi and yeast; since the main factor for sugar syrup preservation is water activity due to the high concentration of sucrose as proposed in this invention and not mineral contents as stated in patent GB984713. Also, the syrup's higher temperature during its processing contributes to its preservation, with the advantage of reducing the hydrodynamic and production cost problems which have already been mentioned.
U.S. Pat. No. 4,193,817 from year 1980, describes only the bleaching processes in liquid sugar syrups to be used in the bottled beverage industry, prepared from refined sugar mixed with standard sugar. The bleaching process is carried out in a semi-continuous way in columns with strong-base anion exchange resins in the form of chloride. This process, however, does not consider the parameter of ashes nor the degree of inversion of sugars contained in the product, which are important parameters to be controlled in the manufacturing of some beverages. Instead, our invention refers to a process that considers the removal of ashes without substantially increasing the content of inverted sugars in the product.
New resins with improved characteristics have come up, such as those presented in U.S. Pat. No. 4,950,332 of 1990, which mentions an adsorbent resin based on a macro porous copolymer used to bleach watery solutions of sugars, standing out for its advantages with the resins of U.S. Pat. No. 2,578,938, U.S. Pat. No. 3,122,456, and U.S. Pat. No. 4,193,817, arguing that all of them have lower adsorbency that carbon. However, this patent also addresses only bleaching of sugar solutions and does not cover the ash removal aspect, while our invention considers both the removal of color and ashes. Patent WO9103574 from year 1991, describes the process required to purify sugar solutions through bleaching, using anion exchange resins or reticulated porous mono vinyl; followed by a decationizer process based on cation exchange resins. This patent basically claims the type of resins developed for the bleaching process and does not cover the demineralization and sugar inversion aspects, which are considered in our invention.
A more recent invention, WO9850588 from 1998, describes a process to purify sugar solutions, which consists of bleaching and demineralizing sugar solutions without need of using cation exchange resins or activated carbon. The process includes contact phases of the sugar solution with a macro porous polymer adsorbent with cationic functional sites in order to complete the demineralization process. In this patent, as well as in the aforementioned ones, the innovations focus on the development of adsorbing resins and polymers to improve their characteristics and functional properties unlike this patent application which proposes a full process starting from raw granulated cane sugar in order to obtain sugar syrup, which, without using activated carbon in the bleaching process, allows controlling of color, of ash content and of inverted sugars in the product, at a lower cost and obtaining similar characteristics than those of syrups prepared from refined sugar.
Likewise, this invention proposes a purification process of syrup prepared with raw granulated cane sugar, by means of dissolving granulated sugar, filtering, bleaching and demineralizing it by ionic exchange, polishing and sanitizing it with ultra violet rays.
The process proposed in this invention enables the obtention of a product with similar characteristics as the solutions prepared from refined cane sugar and offers the user the advantage of an easier to use product, avoiding the sugar dissolution and conditioning processes, thus having an impact in the reduction of production costs.